# Questions tagged [rf]

Short for Radio-Frequency. Frequencies at which radiation (intentional or not) plays a role. Typically associated with wireless communications, but also relevant for high-speed PCB design.

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### How are S-Parameters and Reactance related, can one be calculated from the other?

I know that, for example, $X_L=2\pi f L$ will calculate reactance of an ideal inductor, but can this be calculated for a real component model? Given the S-Parameter values at some frequency from an ...
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I have a big design imported from Altium into HFSS 3DLayout with several RFIC that I want to simulate. RF and Digital (SPI) nets are included in this design. I'm interested mainly in the RF side of ...
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How to calculate the power (dBm) of this signal which is fed into a receiver with an input impedance of 50 ohms? The power in dBm formula is 10log(Vrms^2/R)/1mW and R equals 50 ohms. In this case how ...
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### With given impedance matching network, how to find the possible matchable load impedance range

I have some questions regarding this schematic using Keysight ADS here. The matching network is intended to function at 13.56MHz. The shunt capacitor has a range of 150-1500pF capacitance and the ...
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### How is this possible: Crystal filters for FM signals?

I am trying to make my own superhet reciever. I have achieved downconversion and I am trying to build a crystal filter that will only allow the crystal's resonant frequency through. In doing so, I had ...
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### Antenna port S11(dB) > 0

I'm simulating a microstrip patch antenna in microwave office at 35 GHz. When plotting the S11 in dB of the antenna port I get values greater than zero at frequencies below 28 GHz. How is this ...
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### What is the appropriate name for a parabolic antenna with a "center mounted feed"?

How would a parabolic antenna with a "center mounted feed" be called? Below are some images which illustrate the type of parabolic antenna I'm referring to. According to wikipedia these are ...
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### Unable to interface XBEE with m3pi

I have a m3 pi pololu bot (lpc1768 controller) with a mbed slot. I want to send data from a XBEE S1 connected to my PC to the bot (through another XBEE mounted on it). To achieve this, I've a python ...
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### Method for building a test fixture for the 4294A impedance analyzer?

I have an Agilent 4294A, a 40Hz-110MHz impedance analyzer, but no test fixtures to use. Unfortunately the official test fixtures are out of my price range so I need to build some. After reading ...
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### Analog television: What is the difference between the first IF and second (demodulated) IF?

I am trying to understand what kind of changes occur to a signal in the chips which sit between the tuner and, for example the FM audio demodulator. Take the attached example - the TDA2546A. It takes ...
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### Frequency Counter Input Impedance

I have been looking at RF frequency counters and noticed that they all have one port that says up to 50 MHz with an input impedance of 1 megaohm. However the +50 MHz input says 50 Ohm impedance. If ...
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### Power combiner for I-Q signals in a transmitter

I have a transmitter project to implement. Part of the project is to combine an in-phase and an out of phase (90 degree difference) signal with a center frequency at 3.5GHz. I figured I could ...
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### Simple Diode Mixer Help

Edit: Thank you for your input @Kevin White, much better results with 100 ohm injection resistors, a 1K resistor for a DC pathway and a 1K bias resistor from Anode to +5V. I am an RF enthusiast that ...
43 views

### Can I solder a wire antenna to the exposed PCB antenna of a BBC Micro Bit to boost its bluetooth signal?

Can I solder a wire antenna to the exposed PCB antenna of a BBC Micro Bit to boost its Bluetooth signal for both transmitting and receiving data? Can I solder this type of 2.4G antenna to boost the ...
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### Achieving good S22 for RF Power Amplifier with minimum power loss

I understand that achieving a S22 can reduce the maximum power and efficiency that can be achieved in a Power Amplifier. Is there any systematic approach to achieve <-10dB S22 while minimizing the ...
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### Are there any sample reference RF boards for 15 GHz? [closed]

I'm working on our RF project frequency up-to 15 GHz for our application. We are little concerned about the impedance matching, track width, signal trace routing from top to middle layer, trace ...
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### The problem with sensitivity time controlled (STC) based on pin diode

I'm using sensitivity time controlled (STC) pin diodes of PN:MPP 4201A-206 for our applications. Our operating frequency from 1300 MHz to 1400 MHz. See the schematic diagram below. As device ...
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### What is the link between conjugate matching efficiency and amplifier efficiency?

In the design of a class AB amplifier, there is part of the understanding that I miss. It is well-known that the maximum power transfer is achieved when the load impedance is the complex conjugate of ...
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### I want to Implement this active inductor design in my circuit

I'm trying to use the active inductor in here instead of the inductor in my class e power amplifier, however I'm having difficulties in getting the required values for the parameters in here Cds, Cgs, ...
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### Trying to build RF comb generator based on a schematic. Please help me pick types of components and figure where to purchase them [closed]

I am trying to build this RF comb generator. I've located links for the following: Q1 (BFS17): https://www.aliexpress.com/item/4001097379501.html?spm=a2g0o.productlist.0.0.405918830Mab95&...
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### Output reflection coefficient of a power amplifier

I'm struggling to understand the implication of a poor large signal reflection coefficient at the output of a power amplifier. I designed a power amplifier and checked the large signal S22 (for the ...
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### Motor driver blanks out AM/FM radio reception

Story I do many restorations of 'boomboxes' (70s/80s/90s) especially the decks inside these units. Next to the common problems with belts, gears, pinch rollers, rubber rings etc there is another issue ...
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I'm building a homemade software-defined GPS receiver. I'm currently at a point where I can acquire and track strong signals but struggle to even detect weak signals. I've ruled out problems with my ...
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I am designing a receiver antenna for a wireless power transfer application. The transmitter is a 2m x 2m horn antenna array that transmits a power signal at a frequency of 35 GHz from 100 meters away ...
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First of all I'm quite new to the subject of electrical engineering (I'm a software engineer) especially to RF! so forgive me if I forgot something to add to this question. I've done the research but ...
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### Audio noise when transmitting radio packets using the ESP32

I am building a sort of walkie-talkie using an ESP32 WROOM chip. I use the internal ADC to sample the microphone and the internal DAC to power small headphones. This all works OK, not the highest ...
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### How to choose a sweep range for a known and unknown device with a VNA?

I'm trying to determine best practices for using a VNA to measure say, an antenna. Let's say I have a known antenna with a spec sheet that says it's frequency range is between x and y. Should I set ...
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### Costas Loop QPSK/4QAM

I can use a Costas Loop, modified for QPSK/4QAM and recover the frequency and phase successfully when using a pattern of all 1s or all 0s or a pattern that is repetitive for each I and Q data rail (in ...
1 vote
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### Class AB RF Amplifier with only one active device

I'm designing an amplifier for the 420-440MHz band. I'm looking at using the following part from Ampleon: BLP15H9S100. I'm new to doing RF amplifier work and I've been going through the design process ...
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### Allow 12v power through when RF transmitter is close

I'm currently working on a project to allow 12v power through when a RF Transmitter is within a 20 foot range and shuts off then the transmitter is out of range, I'm not so concerned about the range ...
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### RF high power amp bias scheme

I am using the TGA2237-SM for the TX side in a front end design. I am trying to figure out an analog method for doing the bias up and bias down procedures. Bias up Set gate to Vg=-5V Increase Vg till ...
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### Bandpass filter doesn't work when implementing PCB

I have been trying to make a 5th-order Chebyshev filter going from 500 MHz - 570 MHz and a 3rd-order Chebyshev filter going from 500 MHz - 540 MHz. This is my first time making a filter into a PCB. No ...
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### Diode SPICE data accuracy at high frequencies?

I'm trying to do a non-linear harmonic balance simulation on a schottky diode model MACOM MA4E1317 that according to the manufacturer is usable up to 80 GHz. I got the SPICE data and S-Parameter files ...
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### Synchronized two frequency source seems to have phase drift

I have two arbitrary waveform generators which are synchronized at the external but shared 10 MHz clock. My research experiment importantly uses phase-sensitive signals. The problem I observed is that ...
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### Antenna feed trace keep it short or long?

I am designing a GPS module but am quite new to RF design. I have seen a number of people say to keep your antenna feed line as short as possible. But in the design guide of the GPS module I am using, ...
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### Designing GPS matching network with TESEO and chip antenna

I am new to designing for RF and have a question regarding the design of the matching network for a GPS module I am working on. The datasheet of the chip antenna ANT161575ST-1202A1 recommends a ...
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### Isolating RF Ground is it wise?

I am designing a GPS module and I am planning to isolate the RF GND from the DC power supply GND with an inductor. I have chosen the Murata LQW18CN4N9D0ZD because the low inductance will have low Ldi/...
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### Does an antenna have to be impedance matched to its transmitter circuit or the transmission line from it?

I am still very new to RF and I am trying to understand Impedance matching, so my question could be stupid. I have already learned the basics of it, I know how to use Smith charts, which components to ...
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### How to prototype with sensitive electrical components without a PCB?

Right now I'm trying to get consistent radio operation with an NRF24L01+ and a Teensy 3.6, however in my experience working with radios they have extremely inconsistent connectivity when using ...
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### Is this circuit measuring the electrical field?

I have found the following circuit on the web (https://electroclinica.org/2018/03/23/fabricacion-de-un-sencillo-medidor-de-campo-de-rf-diy/) which claims to be an "RF field" detector/meter/...
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### Interaction between half wave dipole and power supply lines in 433 MHz RF module

For a second iteration of the 433 MHz transmission between Espressif ESP8266 modules, I switched to RF modules based on the SYN115 and SYN480R devices. Largely because these work much better with the ...
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### Chip antenna ANT161575ST-1202A1 layout question

I am designing a GPS module using the following chip antenna: https://product.tdk.com/en/system/files?file=dam/doc/product/rf/rf/antenna/catalog/rf_ant_ant161575st-1202a1_summary_en.pdf The datasheet ...
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### Why are three inductors and one capacitor needed to bias this transisor (radio frequency)?

Below is the circuit. I don't understand its purpose.
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### How to measure radio wave penetration and reflection through different mediums

I would like to do a few experiments to test how different EM radiation frequencies (915 MHz to 5 GHz) interact with 3D print filament materials (like PLA, PolyCarbonate, TPU, etc...). Specifically I ...
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### Maximum RF power for microstrip

Microstrip line have couple parameters that we can change. It's track width (W), copper thickness (t) & substrate thickness (h). The question is "How much RF power we can transfer by this ...
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### Why is ESP32 BLE so power hungry?

The ESP32 consumes around 100-130mA when BLE is active and transmitting, while other BLE chips like nRF8001 only consume around 13mA when BLE is active and transmitting. Am I missing something, or ...
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### When to employ RF shield cover on PCBA?

During reparations and teardowns I have frequently come across PCB-mounted RF shields and covers. While I don't typically work with GHz processors or design RF modules I wonder if such covers could be ...
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### What energy/fields if any is generated when radio frequency is passed through a coaxial cable?

I am new here. Just had a question wondering if someone could answer. Let's say I have a generator that can generate RF and send it through a cable (coaxial) if I attached the end of that wire to a ...
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### How to simplify matching network LC circuit

I'm relatively new to RF design, and trying to implement a Micrel reference PCB antenna design (Heli-2). I am using a MICRF113 RF transmitter at 315MHz to transmit digital data using ASK (OOK). Here ...
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